The taxonomy and phylogenetics of the human and animal pathogen Rhinosporidium seeberi: A critical review.

MedLine Citation:

PMID:
22504725
Owner:
NLM
Status:
Publisher

Abstract/OtherAbstract:

Rhinosporidum seeberi is the etiologic agent of rhinosporidiosis, a disease of mucous membranes and infrequently of the skin and other tissues of humans and animals. Because it resists culture, for more than 100 years R. seeberi true taxonomic identity has been controversial. Two new hypotheses in a long list of related views have been recently introduced: 1) a prokaryote cyanobacterium in the genus Microcystis is the etiologic agent of rhinosporidiosis, 2) R. seeberi is a eukaryote pathogen in the Mesomycetozoa. The reviewed literature on the electron microscopic, the histopathological and more recently the data from several molecular studies strongly support the view that R. seeberi is a eukaryote pathogen. The suggested morphological resemblance of R. seeberi with the prokaryote genus Microcystis is merely hypothetical and lacked the scientific rigor needed to validate the proposed system. A fundamental aspect against the prokaryote theory is the presence of nuclei reported by numerous authors and updated in this review. Moreover, Microcystis's ultra-structural and key cell cycle traits cannot be found in R. seeberi parasitic phase. The PCR amplification of a cyanobacteria 16S rDNA sequence from cases of rhinosporidiosis, while intriguing, will be viewed here as an anomaly due to contamination with environmental Microcystis or perhaps as an endosymbiotic acquisition of plastids from cyanobacteria ancestors. Thus, even if R. seeberi possesses prokaryote DNA, this does not prove that R. seeberi is a cyanobacterium. Further studies are needed to validate R. seeberi's acquisition of prokaryote plastids and other issues that still need careful scrutiny.